1. Field of the Invention
The present invention relates to a controller of an in-cylinder injection engine that pressurizes fuel to high pressure and supplies the high-pressure fuel to a fuel injection valve with a high-pressure pump, the fuel injection valve injecting the fuel directly into a cylinder.
2. Description of Related Art
An in-cylinder injection engine that injects fuel directly into a cylinder has a shorter period from injection to combustion than an intake port injection engine that injects the fuel in an intake port. Accordingly, the in-cylinder injection engine cannot have a sufficient period to atomize the injected fuel. The in-cylinder injection engine has to atomize the injected fuel by increasing injection pressure to high pressure. A certain in-cylinder injection engine pressurizes fuel, which is drawn by a low-pressure pump from a fuel tank, to high pressure with a high-pressure pump driven by a camshaft of the engine and pressure-feeds the fuel to a fuel injection valve with the high-pressure pump, for example, as described in JP-A-2003-322048. The in-cylinder injection engine senses pressure (fuel pressure) of the fuel supplied to the fuel injection valve with a fuel pressure sensor and feedback-controls a discharge amount of the high-pressure pump (valve closing time of a fuel pressure control valve) to conform the sensed fuel pressure to target fuel pressure.
In the in-cylinder injection engine, an injection amount of the fuel injection valve is controlled with an injection period (injection pulse width) as in the intake port injection engine. Even if the injection period is the same, the actual injection amount varies when the fuel pressure changes. Therefore, a fuel pressure correction coefficient is set in accordance with the fuel pressure sensed by the fuel pressure sensor, and a basic injection period calculated in accordance with an operating state of the engine is corrected with the fuel pressure correction coefficient. Thus, the injection period is set in consideration of the change in the fuel pressure.
In order to absorb the variation in the injection amount due to a tolerance or a temporal change of the fuel injection valve and the like, a fuel pressure correction technology described in JP-A-H09-209804 integrates a fuel pressure change sensed by a fuel pressure sensor and performs fuel pressure correction of an injection period with the integration value of the fuel pressure change.
A fuel pressure correction technology described in JP-A-H09-195819 corrects injection start timing based on a difference between fuel pressure sensed by a fuel pressure sensor and target fuel pressure.
There is an injection waiting period from injection setting time, at which an injection period or injection start timing is set, to injection start time. If the high-pressure pump discharges the fuel during the injection waiting period, the actual fuel pressure can increase, so that the actual fuel pressure to occur at the injection start time becomes higher than the pressure at the injection setting time.
Even if the fuel pressure correction of the injection period or the injection start timing is performed with the fuel pressure and the like sensed by the fuel pressure sensor at the injection setting time (or before) as in JP-A-2003-322048 or JP-A-H09-209804, there is a possibility that the actual fuel pressure at the injection start time fluctuates from the actual fuel pressure at the injection setting time (injection period calculation time), deteriorating accuracy of the fuel pressure correction. Specifically, the fuel pressure fluctuation due to the fuel discharge of the high-pressure pump increases more when the engine is started or when the target fuel pressure changes than when the engine is in a steady operation. Accordingly, the fuel pressure correction accuracy deteriorates more.